Electrical connectors are known which include metal or conductive shells around dielectric inserts housing the plurality of electrical terminals, so that the metal shells shield the terminals and their signal transmissions from the influence of electromagnetic interference (EMI) commonly present in the environment. The metal shells have forward ends which extend beyond the forward ends of the respective terminals within the inserts so to providea complete conductive periphery, are associated one within the other in a plug and receptacle relationship. In order for the terminals of the mating connectors to mate in a precisely aligned manner, the shell forward ends perform initial centering prior to terminals engaging each other, and a controlled radial spacing is defined between the plug shell foward end and the receptacle shell forward end therearound when mated. The shells are electrically interconnected by a grounding means which commonly comprises a plurality of spring portions attached in strip form to one of the shells near its forward end, so that the spring portions extend radially to be engaged by the other shell upon connector mating, whereafter the spring portions remain under slight spring bias commoning the shells with each other at a plurality of locations completely surrounding the terminals mated at the mating interface of the connectors. Most commonly such spring strips are secured to the plug-type shell, around and facing radially outwardly from the forward end for the outwardly extending spring portions to engage the inside surface of the receptacle-type shell upon connector mating.
Conventional securing techniques include welding, bonding, swaging, magneforming and soldering, such as in U.S. Pat. No. 4,673,236 wherein a pair of strips with mutually offset spring arms are secured within a shell recess by spot welding. Mechanical securing of EMI spring strips commonly involves special shell structure beyond a simple annular recess, or special assembly steps, or both: examples are found in U.S. Pat. Nos. 4,512,623 and 4,655,533 in which leading and trailing edges of the annular strip disposed in an annular shell recess are secured beneath undercuts of the recess walls to hold the strip to the shell; U.S. Pat. Nos. 4,428,639 in which an inwardly directed flange of the strip's trailing edge is mechanically held against a radical shell flange by being wedged by a compression ring having been deformed; and U.S. Pat. Nos. 3,678,445 and 4,248,492 in which outwardly extending spring tabs at the strip's trailing edge abut against a radial shell flange urging a leading strip edge against a ledge or beneath an undercut. In U.S. Pat Nos. 4,239,318, 4,326,768 and 4,470,657 the ends of the EMI spring strips are fastened, soldered, or welded together to define bracelet-like annular strips which are continuous and elastically flexible to be stretched while being mounted over the forward shell end and seated within an annular recess having an outer diameter slightly larger than the inner diameter of the strip when unstreteched.
One electrical connector is sold by AMP Incorporated, Harrisburg, Pa. under the trade designation ARINC 600 Connector, Part No. 213011-1in which a plug-like metal shell of the connector has secured around its periphery an EMI strip of spring fingers, which strip is located within an annular recess near the shell forward end and bonded in place by adhesive material. Within the recess is a small annular ridge which comprises a strip locating means, and the EMI strip has a continuous annular body section which includes an outwardly extending ridge defining a groove along the inside surface within which the shell ridge is received, locating and aligning the strip prior to bonding. The EMI strip includes both forwardly and rearwardly extending spring fingers where the forwardly extending fingers first engage a mating receptacle-type shell leading end before the electrical contacts within the connectors engage, and the rearward fingers continuously engage the mating shell's inside surface after mating.
In U.S. Pat. No. 4,529,257 an annular EMI grounding member is seated within an annular recess of a plug-type shell in one embodiment and comprises a continuous coil spring partially embedded within an intermediate portion of a sleeve-like ring of elastomeric material in which leading and trailing portions of the ring sealingly engage surfaces of the mated connector shells, while exposed surfaces of the coil spring engage surfaces of the mated shells, whereby the member simultaneously provides grounding and environmental sealing between the connector shells.
It is desirable to provide an EMI spring strip for a connector shell which is easy and economical to assemble.
It is desirable to provide such an EMI spring strip which is securable to a shell requiring only simple structural features on the shell.
It is desirable to provie an EMI spring strip not required to be joined to be continuous prior to assembly nor to require bonding, welding, soldering or the like to the shell.
It is further desirable to provide an EMI spring strip which is easily removable from and replaceable on the shell.